Interworking functions for the Global System for Mobile Communications (GSM) are known from pages 102 and 149-154 of the book "The GSM" published in 1992 by M. Mouly and M.-B. Pautet through their own publishing company, 49 rue Louise Bruneau, 91120 Palaiseau, France. The adaptation means described therein carry out so-called "Interworking Functions" in order to adapt the data signals of data transmissions between the mobile radio network and a telecommunications network to the protocols and modulation rates used in these networks. Accordingly the adaptation means which carry out the "Interworking Functions" are used for the reciprocal adaptation of different data transmissions. The third paragraph on page 149 of the book "The GSM" describes for example that these "Interworking Functions" can be implemented in any mobile radio station. It furthermore describes that the "Interworking Functions" can be implemented in a centralized interworking function which is connected to several mobile radio switching centers. It does not describe the structure of the mobile radio network identified as a "centralized approach".
These adaptation means identified as "Interworking Functions" are furthermore known from the article "Data Transmission in Digital Mobile Radio Networks" by R. Hinz, which appeared on pages 37-40 of the magazine "telekom praxis", volume 72, August 1995, published by Schiele and Schon, Berlin. Although it describes different adaptation means, an integration of these in a centralized interworking function is however not described therein.